A Watertown man is dead after a fire tore through an apartment house at 149 Keyes Aveneue Wednesday night.

Watertown police identify the victim as 65 year old William H. Stitt, who lived in Apartment 6 in the building.

An autopsy performed Thursday afternoon revealed that Stitt died from asphyxiation due to carbon monoxide poisoning.

Investigators ruled the fire was accidental and caused by careless use of smoking material.

According to Watertown Fire Department Battalion Chief Dale Herman, the point of origin was what's believed to have been an upholstered chair.

Herman said cigar butts, matches and a lighter were found in the immediate vicinity of the chair.

The fire broke out just after 8 p.m. Wednesday.

Flames and smoke filled the back portion of the building.

The fire began on the first floor near a rear apartment and spread to the upstairs apartments.

As crews entered the building, the vicitim was found dead near the door.

Two cats and some birds were rescued from the fire and no one else was injured, however a fire fighter suffered minor burns.

While the blaze was burning fast, crews were able to get it under control quickly.